<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>模板差值</title>
</head>
<body>
<div id="app">
  <h1>{{ message }}</h1>
    <h1 id="headlevel1">{{ message }}</h1>
</div>

<script>
    let element = document.getElementById("headlevel1");
    let message = "Hello, World!"

    element.innerHTML = message
</script>
</body>
</html>